Conventional stereo uses two speakers that can be conceptualized as being at either end of an imaginary horizontal rod. Conventional stereo reproduces a sound field created by sound sources arranged in the horizontal plane. If the ‘rod’ is rotated by 90 degrees so that the speakers are now vertically aligned, the arrangement has no left/right discrimination, only up/down discrimination. In general, any rotation of the two stereo speakers from pure horizontal can adversely affect horizontal discrimination in the perceived sound field.